The present invention relates to a ghost canceling system for a television signal.
Generally, a television set receives through an antenna a television signal composed by multiplying a directly received signal and delay signals which reach the antenna through several reflecting routes in which the signals are reflected by neighboring geographical features, neighboring buildings, moving vehicles or the like. Due to such delay signals, generally, multiple images may come out in some extent on the received picture. Such delay signals causing the multiple images are called "the ghost" and a phenomenon where large multiple images deteriorate the quality of the picture is called "a ghost obstacle".
Recently, there have been developed several conventional types of ghost canceling systems which cancel the above-described ghost. For example, there are conventional ghost canceling signal generation circuits for use in a ghost canceling filter circuit as shown in FIGS. 1 and 2.
In a conventional ghost canceling signal generation circuit shown in FIG. 1, a video signal including a ghost is supplied through an input terminal 41 to a shift register 42 in which the video signal which creates time series of sequential images. A tap gain control circuit 46 selects the largest tap gain from tap gains inputted through an input terminal 48 and outputs the tap gain to a plurality of multipliers 44. Simultaneously, the tap gain control circuit 46 controls a tap selection circuit 43 which supplies to the corresponding multipliers 44 the output of the respective shift register 42, which output conforms with delay information in the selected tap gain. All outputs of the multipliers 44 are added to one another by an adder 45, then the adder 45 outputs a ghost canceling signal to an output terminal 47.
On the other hand, in another conventional ghost canceling signal circuit shown in FIG. 2, a video signal including a ghost is supplied to a plurality of variable delay lines 52 through an input terminal 51. A delay amount of the signal supplied to the variable delay lines 52 is controlled by a tap gain control circuit 55 in accordance with a tap gain supplied through an input terminal 57. Each output of the variable delay lines 52 is multiplied with a tap gain outputted from the tap gain control circuit 55. All the outputs of the multipliers 53 are added to one another by an adder 54 which outputs the added signal performing as a ghost canceling signal to an output terminal 56.
The conventional ghost canceling system shown in FIG. 1 is disadvantageous in that the circuit requires a large number of the shift registers 42 and the corresponding output tap for a range of the ghost, the number of which may be larger than several hundreds. Further, the tap selection circuit 43 necessitates a number of input taps equal to that of the output tap of the shift registers 42. Hence, the components of the circuit are disadvantageously large in number and, therefore, the circuit may be intricate. A total cost for the circuit would be unduly disadvantageously increased.
On the other hand, the conventional ghost canceling system shown in FIG. 2 is so constructed that one variable delay line corresponds to one multiplier. Therefore, if there are n tap gains arranged in series n circuit necessitates the corresponding delay lines. However, an actual delay circuit may merely require a shift register having n stages. Thus, such a conventional ghost canceling system is disadvantageous in that a large number of components are necessary and, therefore, a total cost for assembling the circuit is unduly increased.